Effect of Ethanol and Temperature on Partition Coefficients of Ethyl Acetate, Isoamyl Acetate, and Isoamyl Alcohol: Instrumental and Predictive Investigation

Abstract

For alcoholic beverages such as beer, downstream processing for either dealcoholization or off-flavor removal requires both quantitative data and suitable predictive methods. Along with experimental investigations, we use a method initially developed for studying the solubility of gases in two or more miscible liquid solvents to monitor the effect of ethanol on air–water partition coefficients of three major flavors found in beer, namely, isoamyl alcohol, ethyl acetate, and isoamyl acetate. In the ethanol concentration range between 0 and 0.1 mole fraction, a slight, rather linear increase in the Henry’s solubility coefficient was observed. This overall behavior can be captured well using Henry coefficients for aqueous binary and ternary systems together with the Wohl expansion for excess Gibbs free energy coupled with the one-parameter Margules equation. Based on the developed model, the Wohl’s expansion parameter for ethanol–water is introduced as the solvent–solvent interaction parameter. The van ’t Hoff parameters for temperature dependence of Henry coefficients for binary water–flavor solutions are determined in the range of 30 to 60 °C.

A new approach for balancing the microbial synthesis of ethyl acetate and other volatile metabolites during aerobic bioreactor cultivations

“…The partition coefficient is usually measured for water/air systems (see Supporting Information 2), but dissolved substances such as minerals, sugar and other organics can exert a high influence on [7, 19, 49−56]. Hence, values for a given medium/air system have to be determined experimentally.…”

“…Aprea et al. [55] and Ammari et Schroen [56] showed that the presence of ethanol in the aqueous phase increases ; ethanol obviously heightens the ester solubility in water. This observation is important since ethanol may emerge as a by‐product during cultivation.…”

“…The partition coefficient as an important parameter for this ester balancing depends on many factors such as the considered VOC [7, 46−48], the temperature [7, 19, 23, 35, 48], and the presence of other dissolved compounds like minerals [49−52], sugars [19, 53, 54] and other organic substances [55, 56]. This means that the partition coefficient in a real culture medium/air system can significantly differ from the partition coefficient in a water/air system [7, 19].…”

Alternative Perspective on Rapid Wine Oxidation through Changes in Gas-Phase Volatile Concentrations, Highlighted by Matrix Component Effects

“…Given the fact that the partition coefficient is strongly dependent of temperature under which the measurement was taken, values are thus not directly comparable. The temperature dependence of partition coefficients can be mathematically modelled using the van 't Hoff equation 41 :…”

Understanding the lost functionality of ethanol in non-alcoholic beer using sensory evaluation, aroma release and molecular hydrodynamics

“…Hence, recent studies are now beginning to characterise some of the more complex interactions underpinning the partitioning of aroma compounds from the bolus during the oral processing pathway [24][25][26][27] . However, like most studies on food, the majority of research on beer examines the influence of ethanol on the partitioning of individual aroma compounds in water/ethanol solutions 28,29 , although one has examined flavour release in a model beer 17 . Furthermore, to the best of the author's knowledge no studies to date have investigated flavour interactions during oral processing in a real beer matrix and, in particular, a non-alcoholic one.…”